Rollup merge of #124067 - RalfJung:weak-lang-items, r=davidtwco

weak lang items are not allowed to be #[track_caller]

For instance the panic handler will be called via this import
```rust
        extern "Rust" {
            #[lang = "panic_impl"]
            fn panic_impl(pi: &PanicInfo<'_>) -> !;
        }
```
A `#[track_caller]` would add an extra argument and thus make this the wrong signature.

The 2nd commit is a consistency rename; based on the docs [here](https://doc.rust-lang.org/unstable-book/language-features/lang-items.html) and [here](https://rustc-dev-guide.rust-lang.org/lang-items.html) I figured "lang item" is more widely used. (In the compiler output, "lang item" and "language item" seem to be pretty even.)

compiler/rustc_mir_transform/src/deduce_param_attrs.rs

@@ -160,7 +160,7 @@ pub fn deduced_param_attrs<'tcx>(
         return &[];
     }
 
-    // If the Freeze language item isn't present, then don't bother.
+    // If the Freeze lang item isn't present, then don't bother.
     if tcx.lang_items().freeze_trait().is_none() {
         return &[];
     }

compiler/rustc_mir_transform/src/lower_slice_len.rs

@@ -21,7 +21,7 @@ impl<'tcx> MirPass<'tcx> for LowerSliceLenCalls {
 pub fn lower_slice_len_calls<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
     let language_items = tcx.lang_items();
     let Some(slice_len_fn_item_def_id) = language_items.slice_len_fn() else {
-        // there is no language item to compare to :)
+        // there is no lang item to compare to :)
         return;
     };